Powertrain of an internal combustion engine with piston and connecting rod

ABSTRACT

To improve a powertrain of an internal combustion engine with a piston ( 3 ) and connecting rod ( 1 ), in which the connecting rod ( 1 ) connects the piston ( 3 ) on one side on the connecting-rod head ( 2 ) and the corresponding crank pin of a crankshaft on the other side under formation of a connecting-rod eye ( 8 ) via two end bearing arrangements, such that the bearing of the piston ( 3 ) on the connecting-rod head ( 2 ) is improved under maintenance of all previous functions and especially a piston assembly/disassembly is made possible without expensive tools, the bearing arrangement for connecting the piston ( 3 ) to the connecting-rod head ( 2 ) is configured under formation of a positive fit as the ball bearing/universal ball joint ( 11, 13 ), such that on one side a universal ball joint part ( 11 ) is provided with a spherical outer surface ( 12 ) as the bearing surface, which is immersed in lubricating means, and on the other side, is enclosed by a correspondingly spherical pot-like end plate ( 13 ) as the support part for axial support, and the ball bearing/universal ball joint ( 11, 13 ) for maintaining the positive fit includes detachable rotational securing means ( 16   a, b;    17   a, b;    23   a, b ), which also allow in the released state an unlocking of the positive fit by turning the piston ( 3 ) about its axis.

FIELD OF THE INVENTION

The present invention relates generally to powertrains for internal combustion engines, and more particularly, to an improved connecting rod and piston arrangement for use in such engines

BACKGROUND OF THE INVENTION

The connecting rod of internal combustion engines typically consist of a connecting-rod shank and two end bearings, which link the piston and the corresponding crank pin of a crankshaft to a powertrain. One end performs oscillating motions, the other moves with the crank pin in the crank circle, so that a so-called “violin-shaped connecting rod,” i.e., a violin-shaped motion curve of the connecting rod, is created.

From DE 35 05 964 C1, a powertrain with a connecting rod is known, which comprises, in a typical way, an end bearing in the form of a connecting-rod head, i.e., the upper connecting-rod eye, a connecting-rod shank, and an opposite end bearing in the form of the connecting-rod bearing, i.e., the lower connecting-rod eye. Such an arrangement represents a connecting-rod element between the straight part of a crank drive, thus to the piston, and the crankshaft. The connecting-rod head can be complete or in parts. The bearing cover of the divided connecting-rod bearing, thus of the lower connecting-rod eye, is connected to the connecting-rod foot by at least two fitted strain screws. The connecting-rod bearing is formed by the connecting-rod foot and connecting-rod cover, in which bearing shells expand into a complete bearing sleeve. In addition, such connecting-rod bearing receives the crank pin and associated impact-like stresses when the pressure changes, which produce high bearing loads. Because the connecting rod must be guided partially through the engine cylinder when the piston is assembled, at least for a strong crank pin the lower connecting-rod eye or the connecting-rod shank generally had to be divided.

The piston operates under great mechanical and thermal loads. At the same time it must perform several tasks, such as the conversion of pressure energy into mechanical work, sealing of the cylinder chamber from the crankcase, and straight guidance of the upper end of the connecting rod in so-called trunk piston engines. The bearing of the piston on the connecting-rod head has included a piston bolt in the connecting-rod eye, which transferred the forces evenly between piston and connecting rod. Previously, the position of the piston bolt had been determined by two factors. To prevent tipping motions of the piston, its center of gravity should lie on the axis of the bolt. On the other hand, the piston bolt must be fixed in the center of the shaft of the piston so that the normal force is transferred uniformly to the cylinder wall. Because both demands cannot be satisfied simultaneously, the piston bolt previously had been installed slightly above the center of the shaft.

Large pistons of a known type have been made of two or more parts. Thus, the piston base, e.g., made from steel or case iron, is screwed together with the shaft, e.g., made from special cast iron or an aluminum alloy.

From DE 100 46 214 C1, a powertrain is further known, for which a connecting rod is used in the form of a marine head with a one-part connecting-rod shank (which means savings in terms of weight and cost, compared with a connecting-rod shank divided for assembly reasons), which features a special configuration of connecting-rod bearing for receiving the crank pin, and thus enables a compact construction. For this reason, a smaller overall engine height also is possible and the drawing of the piston through the engine cylinder is eased considerably.

Now there is also the need to optimize the bearing of the piston on the connecting-rod head, which had been effected previously by means of a piston bolt, which transfers the forces between the piston and the connecting rod and the connecting-rod eye. In particular, there is the need to form this piston/connecting-rod connection more compactly and to make the piston assembly even simpler.

OBJECTS AND SUMMARY OF THE INVENTION

Starting with the foregoing background, it is an object of the present invention to provide a powertrain with an improved bearing for the piston on a connecting-rod head.

Another object is to provide a powertrain as characterized above in which piston assembly and disassembly is possible without expensive tools.

A further object is to provide a powertrain of the above kind which is lighter in weight and which can be more economically produced.

In carrying out the invention, the powertrain has a ball bearing/universal ball joint which permits elimination of a piston bolt typically required of the prior art, which substantially reduces oscillating mass. Instead, release of the bearing can be effected by turning the piston about its axis before permitting the piston to be drawn from the engine block without the connecting rod. Hence, division of the connecting rod shank also can be eliminated without necessity for realizing the specially configured connecting rod bearing according to DE 100 46 214 C1. Hence further weight reduction and cost savings can be obtained, as well as lower dynamic operating forces.

Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of a ball bearing/universal ball joint in accordance with the invention;

FIG. 2 is a fragmentary longitudinal section, taken in the plane of line A-A in FIG. 1, of a marine head with an undivided connecting-rod shank and ball bearing/universal ball joint in accordance with the invention;

FIG. 3 is a fragmentary section of the marine head taken in the plane of line B-B in FIG. 1, turned 90° with reference to FIG. 2;

FIG. 4 is a perspective of a powertrain with a bearing arrangement on the piston rod in accordance with the invention;

FIG. 5 is another perspective of the marine head shown in FIG. 3, wherein for unlocking the piston shaft from the piston base, a connecting-rod head, i.e., the universal ball joint, is shown removed from the piston base, i.e., from the end plate; and

FIG. 6 is a perspective of the rotational securing means for maintaining a positive lock on the ball bearing/universal joint according to the invention.

While the invention is susceptible of various modifications and alternative constructions, a certain illustrated embodiment thereof has been shown in the drawings and will be described below in detail. It should be understood, however, that there is no intention to limit the invention to the specific form disclosed, but on the contrary, the intention is to cover all modifications, alternative constructions and equivalents falling within the spirit and scope of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

According to FIG. 2, the connecting rod 1 consists of an undivided connecting-rod head 2 for receiving the piston 3, further an undivided connecting-rod shank 4 attached to the connecting-rod head 2, as well as according to FIGS. 4 and 5 a connecting-rod foot 5, which is connected to this shank and which forms together with a connecting-rod cover 7 fixed to this foot by means of several tension screws or strain screws 6 a, b the connecting-rod bearing or the lower connecting-rod eye 8. For lubricating the connecting-rod head 2 or also for cooling the piston, the connecting-rod shank 4 is drilled through lengthwise for the supply of oil, i.e., an axial oil bore hole 9 via a distribution system 22 opens on the connecting-rod head 2.

In the connecting-rod eye 8 of the connecting-rod bearing (FIGS. 4 and 5) sit two bearing shells 10 a, b, which expand into a complete bearing sleeve and which surround the crank pin, not usually shown here, with the retention of a residual gap in sliding contact.

The bearing of the piston 3 on the connecting-rod head 2 includes a universal ball joint part 11, which has a bearing surface arranged on a partial sphere surface on its outer periphery 12. On the side opposite the spherical surface region of this bearing surface, an annular and correspondingly spherical bearing seat in the form of an end plate 13 or support part is provided, so that the universal ball joint part 11 is held in the bearing seat and can pivot about its universal ball joint center relative to the end plate 13 or relative to the support part. As can also be clearly seen from FIG. 2, the universal ball joint part 11 has a bearing surface, which is arranged on its outer periphery 12 on a partial sphere surface and which extends on both sides of a universal ball joint center plane 14 running through the points, at which the universal ball joint part 11 has approximately its greatest diameter.

In the preferred configuration shown in the drawing, the connecting-rod head 2 is configured as the spherical universal ball joint part 11 and the piston base 15 is configured as the support part 13 with the bearing seat in the form of the end plate, but the reverse configuration would also be conceivable.

In the embodiment (see especially FIG. 2), a two-part piston consisting of the piston top part, the piston base 15, and a piston bottom part, the piston shaft 20, is used. A piston formed in three parts in a known way consisting of piston cap, piston shroud, and piston bottom part can be used in an analogous way. Piston base 15 and piston shaft 20 can be connected to each other by means of several suitable screws 21.

The bottom part 20 of the piston 3 encloses the bottom part of the universal ball joint part 11 in shells shaped approximately as hemispheres. In the change between ignition OT and overlapping OT (in this phase all of the valves are open) of the 4-stroke cycle, the inertial forces due to the piston and the ignition forces are supported either on the piston bottom part 20 or on the piston base 15, so that the previous functions of a (now-eliminated) piston bolt are taken up completely in the bearing according to the invention.

This produces, on the one hand, a more compact construction of the connecting rod, especially of a one-part marine head and piston, and, on the other hand, the universal ball joint part is supported against the end plate, but also uniformly on its periphery.

According to the invention, the ball bearing/universal ball joint 11, 13 for maintaining the positive fit includes releasable rotational securing means, which also allow in the released state an unlocking of the positive fit by turning of the piston 3 about its axis.

It can be seen especially in FIG. 1 (the corresponding labeling is maintained in all of the figures) that the piston 3 (in the present case the piston bottom part 20) also has in the interior for receiving the connecting-rod head 2, and thus in the bearing seat 13 in the circumferential direction, at least two recesses 17 a, b, which are preferably diametrically opposite each other and which are each filled by means of rotational securing elements 23 a, b, respectively (see also FIG. 6), which are also fixed by means of a few screws 24 in the piston, i.e., here in the piston bottom part 20.

The spherical universal ball joint 11, i.e., the spherical connecting-rod head 2, is configured with wall sections 16 a, b, which are flattened according to the recesses 17 a, b and which are supported on the rotational securing elements 23 a, b in the assembled state and thus reliably prevent a relative rotation of the piston 3 to the connecting-rod head 2.

In FIG. 6, both rotational securing elements 23 a, b are again shown in detail. They each can be fixed by means of three screws 24 in the piston 3 in the region of the recesses 17 a, b for filling these recesses 17 a, b, or they can be released for unscrewing the piston 3.

Thus, the essential feature of the invention is a ball bearing/universal ball joint 11, 13, whose bearing body 11 provided with a spherical outer surface 12 and immersed in a lubricating means is held against an annular or partial spherical surface acting towards its axial contact and located in a pot-like recess of the end plate 13 and the separation of the connecting rod 1 from the piston 3 can be realized simply, such that the rotational securing elements 23 a, b are removed, a rotation of the piston 3 relative to the connecting rod 1 by 90° (when two recesses 17 a, b are diametrically opposite, see FIG. 1) leads the spherical surface parts of the connecting-rod head 2 into the recesses 17 a, b and the flattened wall sections 16 a, b of the connecting-rod head 2 are arranged opposite the spherical surfaces of the end plate 13, so that a separation of the positive lock of the ball bearing/universal ball joint 11, 13 is realized and the piston 3 can be easily removed from the connecting-rod head 2.

To guarantee reliable permanent lubrication of the ball bearing/universal ball joint 11, 13 realized as described, at the end of the end plate 13 in front of the spherical surface 18 set for axial contact of the bearing body 11, a lubricating means reservoir 19 is provided, whose engine-side sealing is guaranteed as usual.

The configuration of the ball bearing/universal ball joint 11, 13 according to the invention further improves the direct gas-force introduction into the connecting-rod shank 4. The previous piston bolt can be dropped without a replacement. Therefore, the oscillating mass is reduced significantly (by ca. 20%). The frictional power also becomes smaller overall.

It should also be mentioned that a connecting-rod shank division can basically be dropped, because the drawing of the piston 3 through the engine cylinder can now take place in a simple way when the connecting rod is completely detached. This is associated with further savings in terms of weight and costs. The piston disassembly can be performed without expensive tools (hydraulic tools). Thus, a small overall piston height is possible. 

1. Powertrain of an internal combustion engine with piston (3) and connecting rod (1), wherein the connecting rod (1) connects the piston (3) on one side on the connecting-rod head (2) and the corresponding crank pin of a crankshaft on the other side under formation of a connecting-rod eye (8) via two end bearing arrangements, characterized in that the bearing arrangement for connecting the piston (3) to the connecting-rod head (2) is configured under formation of a positive fit as the ball bearing/universal ball joint (11, 13), such that on one side, a universal ball joint part (11) is provided with a spherical outer surface (12) as a bearing surface, which is immersed in lubricating means, and on the other side is enclosed by a correspondingly spherical pot-like end plate (13) as the support part for axial support, and the ball bearing/universal ball joint (11, 13) for maintaining the positive fit encloses detachable rotational securing means (16 a, b; 17 a, b; 23 a, b), which also allow in the released state an unlocking of the positive fit by turning the piston (3) about its axis.
 2. Powertrain according to claim 1, characterized in that the connecting-rod head (2) is formed as the spherical universal ball joint (11) and the piston base (15) of the piston (3) is formed as the bearing seat of the universal ball joint part (11) in the form of the end plate (13).
 3. Powertrain according to claim 2, characterized in that for forming the rotational securing means of the piston (3) in the interior for receiving the connecting-rod head (2), and thus in the bearing seat (13), in the circumferential direction there are also at least two, especially diametrically opposite recesses (17 a, b), which are filled by means of rotational securing elements (23 a, b), and the spherical universal ball joint part (11) is configured with wall sections (16 a, b), which are flattened according to the recesses (17 a, b) and which are supported on the rotational securing elements (23 a, b) in the assembled state.
 4. Powertrain according to claim 1, characterized in that for permanent lubrication of the ball bearing/universal ball joint (11, 13) the connecting-rod shank is provided with an oil bore hole (9), which opens in a lubricating means reservoir (19) provided at the end of the end plate (13) in front of the spherical bearing surface (18) set for axial contact of the universal ball joint part (11). 